Antiviral acetyl pyridine derivative or said acetyl pyridine derivative in combination with acyclovir

ABSTRACT

The present invention relates to a novel ribonucleotide reductase inhibitor and new combinations comprising an antiviral compound, such as acyclovir, and a thiocarbonohydrazone ribonucleotide reductase inhibitor for the chemotherapeutic treatment of virus infections, especiallly viruses of the herpes group.

This is a continuation of copending application Ser. No. 07/371,877 filed on Jun. 26, 1989, now U.S. Pat. No. 5,021,437.

FIELD OF INVENTION

The present invention relates to new antiviral combinations for the chemotherapeutic treatment of virus infections, especially viruses of the herpes group, and to certain compounds for use in such combinations.

BACKGROUND INFORMATION

During the last fifteen years, various antiviral chemotherapeutic agents have been developed for clinical evaluation. A problem with the development of such agents is that, unlike bacteria, viruses are not free-living organisms and are dependent for replication on the life processes of the host cell which they are infecting. It is therefore highly desirable for the antiviral agent to exert its effect specifically on the replicative processes of the virus rather than on the corresponding processes of normal (non-infected) cells. The antiviral agents so far developed act via a variety of mechanisms to exert their antiviral effects. These mechanisms involve inhibition of different stages in the process of viral replication in the host cells.

One particular stage of replication at which the virus is susceptible to inhibition is the stage of nucleic acid replication, i.e., the production of DNA from DNA, RNA from RNA, or DNA from RNA (depending on whether the virus is a DNA or an RNA virus), where the viral DNA or RNA acts as a template for the production of new DNA or RNA. In the case of DNA viruses, the production of new viral DNA involves the interaction of the enzyme DNA polymerase with the constituent nucleotides (specifically deoxyribonucleotides) which act as building blocks for the new DNA. Antiviral action at this stage generally involves the use of "fraudulent" or deleterious nucleotides which mimic the normal viral materials and either compete for DNA polymerase and/or are incorporated into the viral DNA chain to make it non-functional.

These "fraudulent" or deleterious nucleotides comprise a triphosphate derived from a nucleoside analog which is converted by enzymes first into the monophosphate and then subsequently into the diphosphate and finally into the triphosphate. An example of this type of antiviral agent is the marketed compound, acyclovir, i.e., 9-(2-hydroxyethoxymethyl)guanine (U.S. Pat. No. 4,199,574), which contains an acyclic side-chain in the 9-position of guanine compared with a cyclic sugar residue in this position in guanosine. The antiviral mechanism of action of acyclovir is believed to involve first its conversion to acyclovir monophosphate by the enzyme thymidine kinase, which is specific to herpes-infected cells. Once formed, acyclovir monophosphate is converted by normal cellular enzymes (kinases) via the diphosphate to acyclovir triphosphate (ACV-TP). Acyclovir triphosphate is believed to serve as an inhibitor of viral DNA polymerase since it resembles the natural nucleotide substrate, deoxyguanosine triphosphate (dGTP), and as a result competes with dGTP for binding to the DNA polymerase and thus competitively inhibits the effectiveness of the enzyme and consequently viral replication. When ACV-TP acts as a substrate for DNA polymerase it becomes incorporated into the viral DNA chain, but since it lacks the 3'-hydroxyl group present on the cyclic sugar moiety of the natural nucleotide substrate, it presumably acts as a DNA chain terminator. It also apparently inactivates the viral DNA polymerase. Thus, viral replication is prevented.

The antiviral effect of acyclovir, and related compounds which operate via an analogous mode of action, is believed to involve competitive inhibition, apparent inactivation of the viral DNA polymerase, and termination of the growing DNA chain.

A disadvantageous aspect of a competitive inhibitor is that the normal substrate may accumulate and become more effective in competitively blocking the binding of the inhibitor. In this manner, the build up of, for example, dGTP may hinder the binding of ACV-TP to the polymerase and thereby prevent subsequent inhibition and termination of viral DNA processing.

European Patent Specification 135,713 (U.S. Pat. No. 4,758,572) discloses antiviral combinations of nucleoside analogs and thiosemicarbazone ribonucleotide reductase inhibitors. U.S. Pat. No. 4,719,221 discloses the thiosemicarbazones in European Patent Specification 135,713.

SUMMARY OF THE INVENTION

It has now been discovered that a certain ribonucleotide reductase (RR) inhibitor, as disclosed herein, has anti-herpes virus activity. Furthermore, this RR inhibitor significantly potentiates the efficacy of antiviral compounds, such as acyclovir. The combination of RR inhibitor and antiviral compound has the effect, in virus-infected cells, of decreasing the pool of deoxynucleotide substrate of virus DNA polymerase and, surprisingly, increasing the triphosphate form of the antiviral compound. Thus, the ratio of triphosphate form of the antiviral compound to the competing deoxynucleotide substrate of viral DNA polymerase, such as deoxyguanosine triphosphate, is greatly improved, and the binding of the triphosphate form of the antiviral compound to the viral DNA polymerase is facilitated.

The net result is that the use of a certain RR inhibitor, as disclosed herein, in combination with an antiviral compound of the above described type results in a surprising synergistic increase in antiviral efficacy in comparison with the individual antiviral effects of the components of the combination. The RR inhibitor of this invention is more potent in synergy with acyclovir in vivo and substantially less toxic than the thiosemicarbazone RR inhibitors cited in the above-mentioned European Patent Specification.

OBJECTS OF THE INVENTION

According to a feature of the present invention, there is provided a combination of (1) an antiviral compound which is capable of being converted in vivo, via a metabolic pathway, which includes a step dependent upon virus-induced enzyme, to an inhibitor of, or an alternative substrate for, viral DNA polymerase, and (2) a ribonucleotide reductase inhibitor which is a compound of formula (I), namely 2-acetylpyridine 5-[(2-chloroanilino) thiocarbonyl]thiocarbonohydrazone. ##STR1##

The present invention also provides the above-defined combination for use in medical therapy e.g. the treatment of viral diseases in the human and animal body. Examples of such viral diseases include those caused by viruses of the herpes family, for example, herpes simplex 1 and 2 viruses (HSV 1, HSV 2), varicella zoster virus (VZV), cytomegalovirus (CMV) and Epstein-Barr virus (EBV), but other herpes virus infections can also be treated (e.g. feline herpes virus infections).

The invention further provides a method for the treatment of viral diseases in a human or animal body which comprises administering to the human or animal body an effective non-toxic amount of a combination as defined above. It will be appreciated that, in accordance with the present invention, the antiviral compound and the RR inhibitor may be administered simultaneously (in the same or different pharmaceutical formulations) or sequentially. In the latter case, however, the components of the combination are preferably administered within a sufficiently short interval to ensure that a synergistic antiviral effect is achieved.

The invention further provides use of a combination according to the present invention in the manufacture of a medicament for use in the treatment or prophylaxis of a virus infection, particularly herpes, selected from HSV 1, HSV 2, VZV, CMV and EBV.

The present invention also provides:

a) A method of therapeutically increasing the pool size of a deleterious substrate and/or an inhibitor of viral DNA polymerase in a mammal having a viral infection and receiving an antiviral compound, which depends on viral-induced enzyme(s) for conversion to said deleterious substrate and/or inhibitor in the mammal, and the improvement of administering to said mammal an RR inhibitor of formula (I) or a pharmaceutically acceptable salt thereof in an amount effective for increasing the pool of said inhibitor and/or deleterious substrate of viral DNA polymerase in said mammal; and

b) A method of potentiating in a mammal having a viral infection the antiviral activity of an antiviral compound being administered to said mammal, which depends on viral-induced enzyme(s) for conversion to a deleterious substrate and/or inhibitor of viral DNA polymerase, and which comprises administering to said mammal an effective potentiating amount of an RR inhibitor of formula (I) or a physiologically acceptable salt thereof.

An advantage of the combination according to the invention is that it enables one to obtain an improved antiviral efficacy. Furthermore, a lower dosage of an antiviral compound (compared with the compound used alone) can be efficacious, thereby improving the therapeutic index of the antiviral compound. Thus, for example, the combination may be used to treat conditions which would otherwise require relatively large dosages of the antiviral compound at which toxicity problems may occur.

The combination according to the invention is especially applicable to the treatment of herpes simplex types 1 and 2 infections and varciella zoster virus infections (e.g., shingles).

DESCRIPTION OF THE PREFERRED EMBODIMENT

With regard to the antiviral compound, this can be selected from any compound that is activated in vivo by virus-induced enzyme(s) as defined above. Such compounds are generally substrates for an appropriate kinase enzyme of viral origin which phosphorylates the compounds to form a monophosphate which, per se or in a metabolically transformed form, is then phosphorylated (by kinase enzymes of either viral or cellular (origin) to form the diphosphate and finally the triphosphate DNA polymerase inhibitor or deleterious substrate. The use of an antiviral compound that is selectively phosphorylated by viral enzymes rather than by cellular enzymes provides a greater concentration of the phosphorylated (activated) antiviral compound in infected cells than in non-infected cells. Thus the activated antiviral compound causes selective toxicity to the virus, inhibiting virus replication. It is preferred to use an antiviral compound that is not only a DNA polymerase inhibitor but is also, when incorporated into the viral DNA chain, a chain terminator and, possibly, an apparent inactivator of the viral DNA polymerase.

Thus, for example, acyclovir, as mentioned above, is converted by virus-coded thymidine kinase (but not to any substantial extent by cellular thymidine kinase) to the monophosphate which is then converted to the diphosphate and triphosphate via cellular enzymes. Acyclovir triphosphate is also a DNA chain terminator. The mechanism of acyclovir and other antiviral compounds is described by E. de Clerq in "New Trends in Antiviral Chemotherapy", Archives Internationale de Physiologie et de Biochimie, 87(2), 353-395 (1979) and by P. Furman et al. in "Acyclovir: Mechanism of Action", Human Herpes Infections, edited by C. Lopez and B. Roizman, pp. 129-138, Raven Press, New York (1986).

The antiviral compound employed in the combinations according to the invention may be selected for example from acyclovir and analogs thereof, e.g., those compounds of formula (II) ##STR2## (wherein X is oxygen or sulfur, R is hydrogen, hydroxy or amino and Y is hydrogen or hydroxymethyl) and pharmaceutically acceptable salts and esters thereof.

In addition to acyclovir, examples of preferred compounds of formula (II) for use in the present invention include:

9-[(2-hydroxy-1-hydroxymethylethoxy)methyl]guanine (see U.S. Pat. No. 4,609,662) as well as prodrugs that are converted in vivo into the above compounds, e.g. 2-amino-9-(2-hydroxyethoxymethyl)adenine and 9-[(2-hydroxy-1-hydroxymethylethoxy)methyl]-2,6-diaminopurine. See U.S. Pat. No. 4,323,573 and G.B. Patent 2,104,070.

Alternatively, the antiviral compound may be 1-[2-hydroxy-1-(hydroxymethyl)ethoxymethyl]cytosine or pharmaceutically acceptable salts and esters thereof. See European Patent Specification 167,385.

The above-mentioned nucleoside analogs also include the pharmaceutically acceptable salts, esters, or salts of such esters, or any other compound which, upon administration to a human subject, is capable of providing (directly or indirectly) the antivirally active metabolite or residue thereof. See European Patent Specification 272,065.

The above-defined RR inhibitor of formula (I) and its pharmaceutically acceptable salts are novel and represent a further feature of the present invention, since they have been found to potentiate, in a synergistic manner, the antiviral effects of the antiviral compounds described above. The RR inhibitor of formula (I) also has activity against herpes viruses which renders the compound useful per se in the treatment of herpes virus infections.

Salts of the RR inhibitor, according to the invention, which may be conveniently used in therapy, include pharmaceutically acceptable base salts, derived from an appropriate base, such as alkali metal (e.g. sodium), alkaline earth metal (e.g. magnesium) salts, ammonium and NX⁺ 4 (wherein X is C₁₋₄ alkyl) salts. Suitable pharmaceutically acceptable salts also include, but are not limited to, those prepared from the following acids: hydrochloric, hydrobromic, sulfuric, nitric, phosphoric, maleic, salicylic, p-toluene-sulfonic, tartaric, citric, acetic, methanesulfonic, formic, succinic, naphthalene-2-sulfonic, isethionic, lactobionic and benzenesulfonic. The pharmaceutically acceptable salts of the above RR inhibitors may be prepared in conventional manner for example by treatment with the appropriate base or acid.

The combinations according to the invention may be administered to the subject concerned in conventional manner. As indicated above, the antiviral compound and the RR inhibitor may be administered simultaneously (e.g. in a unitary pharmaceutical formulation) or separately (e.g. in separate pharmaceutical formulations). In general, the combinations may be administered by the topical, oral, rectal or parenteral (e.g. intravenous, subcutaneous or intramuscular) route. The dosage of the combination will depend on the condition being treated, the particular antiviral compound and RR inhibitor concerned, and other clinical factors such as the weight and condition of the patient and the routes of administration of the compounds. However, for administration by the oral route, a dosage of the antiviral compound of 1 to 150 mg/kg/day, more preferably 5-125 mg/kg/day, and most preferably 15 to 80 mg/kg/day, is generally sufficient. The amount of RR inhibitor in the combination will be determined from the amount of antiviral compound specified above and the desired ratio of antiviral compound to RR inhibitor.

The ratio of antiviral compound to RR inhibitor is preferably in the range of about 0.5:1 to 50:1 (w/w), more preferably 1:1 to 30:1 (w/w), and most preferably 5:3 (w/w). Thus when 25 mg/kg/day of acyclovir is administered to a subject, 15 mg/kg/day of 2-acetylpyridine 5-[(2-chloroanilino)thiocarbonyl]thiocarbonohydrazone would also be administered.

For convenience, the antiviral compound and RR inhibitor are preferably administered in a unitary pharmaceutical formulation. Thus, the present invention further provides a pharmaceutical formulation comprising a combination according to the invention, together with at least one pharmaceutical carrier or excipient, the antiviral compound and RR inhibitor being present in the formulation in a ratio whereby a synergistic antiviral effect is achieved.

Formulations include those suitable for oral, rectal, nasal, topical (including buccal and sublingual), vaginal, parenteral (including subcutaneous, intramuscular, intravenous, intradermal, intrathecal and epidural) administration. The formulation may conveniently be presented in unit dosage form and may be prepared by conventional pharmaceutical techniques. Such techniques include the step of bringing into association the active ingredients with the pharmaceutical carrier(s) or excipient(s). In general the formulations are prepared by uniformly and intimately bringing into association the active ingredients with liquid carriers or finely divided solid carriers or both, and then, if necessary, shaping the product.

The compositions of the present invention may additionally contain other adjunct components conventionally found in pharmaceutical compositions, at their art-established usage levels. Thus, for example, the compositions may contain additional compatible pharmaceutically-active materials which enhance antiviral effectiveness or facilitate combination therapy (such as potentiating agents, antivirals, antimicrobials, antipruritics, astringents, local anesthetics or anti-inflammatory agents), or may contain materials useful in physically formulating various dosage forms of the composition of present invention, such as excipients, dyes, perfumes, fragrances, preservatives, antioxidants, opacifiers, thickening agents and stabilizers. These materials, when added, should not unduly interfere with the penetration enhancement of the compositions of this invention. Such formula modifications to improve cosmetic acceptability are well within the skill of workers in the cosmetic and dermatological arts and, by themselves, constitute no part of the present invention.

Formulations of the present invention suitable for oral administration may be presented as discrete units such as capsules, cachets or tablets each containing predetermined amounts of the active ingredients; as powders or granules; as solutions or suspensions in an aqueous liquid or a non-aqueous liquid; or as oil-in-water emulsions or water-in-oil liquid emulsions. A tablet may be made by compression or molding, optionally with one or more accessory ingredients. Compressed tablets may be prepared by compressing in a suitable machine, the active ingredients in a free-flowing form such as a powder or granules, optionally mixed with a binder, lubricant, inert diluent, preservative, surface active or dispersing agent. Molded tablets may be made by molding in a suitable machine a mixture of the powdered compound moistened with an inert liquid diluent. The tablets may optionally be coated or scored and may be formulated so as to provide slow or controlled release of the active ingredients therein.

For infections of the eye or other external tissues, e.g., mouth and skin, the formulations are preferably applied as a topical ointment or cream containing the combined active ingredients in a total amount of, for example, 0.075 to 30% w/w, preferably 0.2 to 20% w/w and most preferably 0.4 to 15% w/w. When formulated in an ointment, the active ingredients may be employed with either paraffinic or a water-miscible ointment base. Alternatively, the active ingredients may be formulated in a cream with an oil-in-water cream base.

If desired, the aqueous phase of the cream base may include, for example at least 30% w/w of a polyhydric alcohol, i.e., an alcohol having two or more hydroxyl groups such as propylene glycol, butane-1,3-diol, mannitol, sorbitol, glycerol and polyethylene glycol and mixtures thereof. The topical formulation may desirably include a compound which enhances absorption or penetration of the active ingredient through the skin or other affected areas. Examples of such dermal penetration enhancers include dimethylsulfoxide and related analogs.

The oily phase of the emulsions of this invention may be constituted from known ingredients in a known manner. While the phase may comprise merely an emulsifier, it desirably comprises a mixture of at least one emulsifier with a fat or an oil or with both a fat and an oil. Preferably, a hydrophilic emulsifier is included together with a lipophilic emulsifier which acts as a stabilizer. It is also preferred to include both an oil and a fat.

Together, the emulsifier(s) with or without stabilizer(s) make-up the so-called emulsifying wax, and the wax together with the oil and fat make up the so-called emulsifying ointment base which forms the oily dispersed phase of the cream formulations.

Emulsifiers and emulsion stabilizers suitable for use in the formulation of the present invention include Tween 60, Span 80, cetostearyl alcohol, myristyl alcohol, glyceryl monostearate, sodium lauryl sulfate, Myrj and Birj.

The choice of suitable oils or fats for the formulation is based on achieving the desired cosmetic properties, since the solubility of the active compound in most oils likely to be used in pharmaceutical emulsion formulations is very low. Thus, the cream should preferably be a non-greasy, non-staining and washable product with suitable consistency to avoid leakage from tubes or other containers. Straight or branched chain, mono- or dibasic alkyl esters such as di-isoadipate, isocetyl stearate, propylene glycol diester of coconut fatty acids, isopropyl myristate, decyl oleate, isopropyl palmitate, butyl stearate, 2-ethylhexyl palmitate or a blend of branched chain esters known as Crodamol CAP may be used, the last three being preferred esters. These may be used alone or in combination depending on the properties required. Alternatively, high melting point lipids such as white soft paraffin and/or liquid paraffin or other mineral oils can be used.

Formulations suitable for topical administration to the eye also include eye drops wherein the active ingredients are dissolved or suspended in suitable carrier, especially an aqueous solvent for the active ingredients. The antiviral active ingredients are preferably present in such formulations in a concentration of 0.5 to 20%, advantageously 0.5 to 10% and particularly about 1.5% w/w.

Formulations suitable for topical administration in the mouth include lozenges comprising the active ingredient in a flavored basis, usually sucrose and acacia or tragacanth; pastilles comprising the active ingredient in an inert bases such as gelatin and glycerin, or sucrose and acacia; and mouth washes comprising the active ingredients in a suitable liquid carrier. Formulations for rectal administration may be presented as a suppository with a suitable base comprising for example cocoa butter or a salicylate.

Formulations suitable for nasal administration wherein the carrier is a solid include a coarse powder having a particle size for example in the range 20 to 500 microns which is administered in a manner in which snuff is taken, i.e., by rapid inhalation through the nasal passage from a container of the powder held close up to the nose. Suitable formulations wherein the carrier is a liquid, for administration as for example a nasal spray or as nasal drops, include aqueous or oil solutions of the active ingredients.

Formulations suitable for vaginal administration may be presented as pessaries, tampons, creams, gels, pastes, foams or spray formulations containing in addition to the active ingredients such carriers as are known in the art to be appropriate.

Formulations suitable for parenteral administration include aqueous and non-aqueous sterile injection solutions which may contain anti-oxidants, buffers, bacteriostats and solutes which render the formulation isotonic with the blood of the intended recipient. Suitable formulations also include aqueous and non-aqueous sterile suspensions which may contain suspending agents and thickening agents. The formulations may be presented in unit-dose or multi-dose containers, for example sealed ampoules and vials, and may be stored in a freeze-dried (lyophilized) condition requiring only the addition of the sterile liquid carrier, for example water for injections, immediately prior to use. Extemporaneous injection solution and suspensions may be prepared from sterile powders, granules and tablets of the kind previously described.

Preferred unit dosage formulations are those containing a daily dose or unit, daily sub-dose, or an appropriate fraction thereof, of the active ingredients.

It should be understood that in addition to the ingredients particularly mentioned above, the formulations of this invention may include other agents conventional in the art having regard to the type of formulation in question, for example, those suitable for oral administration may include flavoring agents.

Antiviral Activity

The ribonucleotide reductase inhibitor of the present invention was shown by use of the dye uptake method described by McLaren, Ellis and Hunter in Antivir. Res. 3, 223-234 (1983) to potentiate the in vitro antiviral effects of acyclovir. Vero cells (20,000 cells/well) were incubated in microtiter wells for 24 hours. Various concentrations of acyclovir and the ribonucleotide reductase inhibitor were added and the cells were infected with 30 infectious particles/well of HSV-1 or HSV-2. After 3 days incubation, the antiviral effects were assessed by determining the prevention of the cytopathic effects of the viruses. Examples of the synergistic antiherpes activity of 2-acetylpyridine 5-[(2-chloroanilino)thiocarbonyl]thiocarbonhydrazone (compound B); and acyclovir (ACV) are given below.

An example of the synergistic antiherpes activity of Compound B and ACV:

    ______________________________________                                                    IC.sub.50.sup.a                                                                                      Fold                                          Compound(s)  Observed  Calculated.sup.b                                                                         potentiated.sup.c                             ______________________________________                                         ACV          1.6       1.6       --                                            ACV plus 0.4 μM                                                                          0.84      1.6       1.9                                           Compound B (0%).sup.d                                                          ACV plus 0.6 μM                                                                          0.62      1.6       2.5                                           Compound B (0%).sup.d                                                          ACV plus 0.9 μM                                                                          0.33      1.6       4.8                                           Compound B (0%).sup.d                                                          ACV plus 1.3 μM                                                                          0.19      1.6       8.4                                           Compound B (0%).sup.d                                                          ACV plus 2.0 μM                                                                          0.15      1.1       7.3                                           Compound B (11%).sup.d                                                         ______________________________________                                          .sup.a Concentration (μM) required to inhibit HSC2 replication by 50%.      .sup.b Theoretical value for the combination of ACV and Compound B.            .sup.c Ratio of calculated IC.sub.50 to observed IC.sub.50.                    .sup.d Parenthetical number is the % inhibition of virus replication by        Compound B alone.                                                        

The following Examples are provided by way of illustration of the present invention and should in no way be construed as limitation thereof.

EXAMPLES RR Inhibitors Preparation 1 2-Acetylpyridine thiocarbonohydrazone

To a solution of distilled 2-acetylpyridine (Aldrich Chemical Co., Milwaukee, Wis. 53233), 33.3 g, in 300 mL of methanol was added thiocarbohydrazide (Sigma Chemical Co., St. Louis, Mo, 63178), 29.18 g. The resulting mixture was heated at reflux, under nitrogen, overnight. A precipitate was collected by filtration, washed with cold methanol, and dried to give 56.0 g (97%) of 2-acetylpyridine thiocarbonohydrazone as a white crystalline solid, m.p. 185°-186° C. (dec.).

¹ H-NMR: (DMSO-d₆) δ2.34 (s, 3H, CH₃), 5.00 (br s, 2H, NH₂), 7.36 (ddd; 1H; J=1.0, 4.9, 7.5; aromatic CH), 7.77 (dt; 1H; J=1.7, 7.8; aromatic CH), 8.53 (m, 2H, aromatic CH), 9.96 (br s, 1H, NH), 10.31 (s, 1H, NH).

Preparation 2 2-Acetylpyridine 5-[(methylamino)thiocarbonyl]thiocarbonohydrazone

A 1 L 3-neck flask fitted with an overhead mechanical stirrer, condenser, glass stopper, and a nitrogen line was charged with 2-acetylpyridine thiocarbonohydrazone, 5.37 g, and 500 mL of absolute ethanol. The resulting mixture was heated at reflux for 5 min to dissolve most of the solid material. The mixture was allowed to cool below reflux temperature and methyl isothiocyanate (Aldrich), 2.20 mL (2.35 g), was added. The reaction mixture was heated at reflux for 30 min, allowed to cool to room temperature, and subsequently cooled in an ice-water bath. A precipitate was collected by filtration, washed with cold ethanol, and dried in vacuo to give 6.74 g (93.3%) of 2-acetylpyridine 5-[(methylamino)thiocarbonyl]thiocarbonohydrazone as a white crystalline solid, m.p. 178.0°-178.5° C. (dec.).

¹ H-NMR: (DMSO-d₆) δ2.39 (s, 3H, COCH₃), 2.86 (d, 3H, J=4, NCH₃), 7.38 (m, 1H, aromatic CH), 7.85 (m, 1H, NH), 8.56 (m, 2H, aromatic CH), 9.43 (br s, 1H, NH), 10.32 (br s, 1H, NH), 10.82 (br s, 1H, NH).

The following compound (Example 1) was prepared using the general method described in Preparation 2:

Novel RR Inhibitor EXAMPLE 1 2-Acetylpyridine 5-[(2-chloroanilino)thiocarbonyl]thiocarbonohydrazone

Reaction of 2-acetylpyridine thiocarbonohydrazone, 7.00 g, and 2-chlorophenyl isothiocyanate (Trans World, Chemicals, Inc., Chevy Chase, Md. 20815), 5.67 g, in 245 mL of dry DMF gave 8.74 g of a tan powder. Recrystallization from DMF/H₂ O afforded 5.69 g (45%) of the title compound as a light yellow powder, m.p. 159°-160° C. (dec.).

¹ H-NMR: (DMSO-d₆) δ2.48 (s, 3H, CH₃), 7.17-8.58 (m, 8H, aromatic CH), 9.39 (br s, 1H, NH), 9.95 (br s, 1H, NH), 10.52 (br s, 1H, NH), 10.96 (s, 1H, NH).

Elemental Analysis: Calcd. for C₁₅ H₁₅ N₆ ClS₂.0.25 H₂ O (mw 383.41, parent mw 378.91): C, 46.99; H, 4.07; N, 21.92; Cl, 9.25; S, 16.72. Found: C, 46.90; H, 4.07; N, 21.88; Cl, 9.25; s, 16.67.

Pharmaceutical Formulations

In the following Examples, the antiviral compound is acyclovir and the RR inhibitor is 2-acetylpyridine 5-[(2, -chloroanilino)thiocarbonyl]thiocarbonohydrazone.

    ______________________________________                                         Tablet             Amount                                                      ______________________________________                                         RR Inhibitor       300 mg                                                      Antiviral Compound 500 mg                                                      Lactose            105 mg                                                      Starch              50 mg                                                      Polyvinylpyrrolidinone                                                                             20 mg                                                      Magnesium Stearate  10 mg                                                                         985 mg                                                      ______________________________________                                    

The active compounds are mixed with the lactose and starch and are wet granulated with a solution of the polyvinylpyrrolidinone. The granules are dried, sifted, and blended with magnesium stearate and compressed.

    ______________________________________                                         Capsule            Amount                                                      ______________________________________                                         RR Inhibitor       300 mg                                                      Antiviral Compound 500 mg                                                      Lactose            100 mg                                                      Sodium Starch Glycollate                                                                           10 mg                                                      Polyvinylpyrrolidinone                                                                             10 mg                                                      Magnesium Stearate  3 mg                                                                          923 mg                                                      ______________________________________                                    

The active compounds are mixed with the lactose and sodium starch glycollate and are wet granulated with a solution of the polyvinylpyrrolidinone. The granules are dried, sifted, and blended with the magnesium stearate and filled into hard gelatin capsules.

    ______________________________________                                         Cream (1)         Amount                                                       ______________________________________                                         RR Inhibitor      6.00 g                                                       Antiviral Compound                                                                               10.00 g                                                      Glycerol          2.00 g                                                       Cetostearyl Alcohol                                                                              6.75 g                                                       Sodium Lauryl Sulfate                                                                            0.75 g                                                       White Soft Paraffin                                                                              12.50 g                                                      Liquid Paraffin   5.00 g                                                       Chlorocresol      0.10 g                                                       Purified Water to 100.00 g                                                     ______________________________________                                    

The active compounds are mixed with purified water and glycerol and heated to 70° C. The remaining ingredients are heated together at 70° C. The two parts are added together and emulsified. The cream is cooled and filled into containers.

    ______________________________________                                         Cream (2)         Amount                                                       ______________________________________                                         RR Inhibitor      6.00 g                                                       Antiviral Compound                                                                               10.00 g                                                      Minerol Oil, Heavy                                                                               5.00 g                                                       Polawax           7.50 g                                                       Propylene Glycol  40.00 g                                                      White Petrolatum  12.50 g                                                      Sodium Edetate    0.10 g                                                       Purified Water to 100.00 g                                                     ______________________________________                                    

A solution of sodium edetate in water is heated to 70°-75° C. and added to a mixture of the mineral oil, white petrolatum and polawax, heated to the same temperature. The propylene glycol is added and the mixture is allowed to cool to 50°-55° C. The two active compounds are added, mixed and allowed to cool to 25°-30° C. Sufficient purified water is added to achieve the proper batch weight. The cream is filled into containers.

    ______________________________________                                         Intravenous Injection   Amount                                                 ______________________________________                                         RR Inhibitor            300 mg                                                 Antiviral Compound      500 mg                                                 Glycerol                200 mg                                                 Sodium Hydroxide solution qs                                                                           pH 7.0-7.5                                             Water for Injections to  10 mL                                                 ______________________________________                                    

The active compounds and the mannitol are dissolved in a part of the water for injections. The pH is adjusted with the sodium hydroxide solution and the solution is made up to volume with additional water for injections. Under aseptic conditions, the solution is sterilized by filtration and filled into sterile vials. Water is removed by freeze-drying. The vials are sealed under an atmosphere of nitrogen and are closed with a sterile closure and a metal collar.

Toxicology

Rats were dosed orally with 2-acetylpyridine 5-((2-chloroanilino) thiocarbonyl)thiocarbonohydrazone, 60 mg/kg 1 day, for 30 days. At 15 and 30 days, the hematological profile of the compound showed less than 10% deviation from control values for all the parameters measured. The rats also had normal colored urine and normal body weight. 

I claim:
 1. In a method of treating a site of a herpes virus infection, the step of topically applying to said infection site 2-acetylpyridine 5-[(2-chloroanilino)thiocarbonyl] thiocarbonohydrazone or a pharmaceutically acceptable salt thereof.
 2. In a method of treating a site of a topical herpes virus infection, in which acyclovir is used to treat the infection, the step of topically applying an effective amount of 2-acetylpyridine 5-[(2-chloroanilino)thiocarbonyl] thiocarbonohydrazone to said site to potentiate the effect of acyclovir.
 3. A method of treating a herpes virus infection in a mammal which comprises administering to said mammal an effective treatment amount of a compound 2-acetylpyridine 5-[(2-chloroanilino)thiocarbonyl]thiocarbonohydrazone or a pharmaceutically acceptable salt thereof.
 4. The method of claim 1, in which the herpes virus infection is HSV1 or HSV2.
 5. The method of claim 4, in which the compound or salt is applied topically.
 6. The method of claim 1, in which the herpes infection is VZV.
 7. The method of claim 6, in which the compound or salt is applied topically.
 8. The method of claim 3, in which acyclovir is also administered to said mammal. 